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//! Pixel-level expression evaluator for raster bands
use super::ast::{BinaryOp, Expr, UnaryOp};
use crate::error::{AlgorithmError, Result};
use oxigdal_core::buffer::RasterBuffer;
#[cfg(not(feature = "std"))]
use alloc::{string::String, vec::Vec};
/// Evaluator for raster expressions
pub(super) struct Evaluator<'a> {
bands: &'a [RasterBuffer],
}
impl<'a> Evaluator<'a> {
pub(super) fn new(bands: &'a [RasterBuffer]) -> Self {
Self { bands }
}
pub(super) fn eval_pixel(&self, expr: &Expr, x: u64, y: u64) -> Result<f64> {
match expr {
Expr::Number(n) => Ok(*n),
Expr::Band(b) => {
if *b == 0 || *b > self.bands.len() {
return Err(AlgorithmError::InvalidParameter {
parameter: "band",
message: format!("Band {} out of range (1-{})", b, self.bands.len()),
});
}
self.bands[b - 1]
.get_pixel(x, y)
.map_err(AlgorithmError::Core)
}
Expr::BinaryOp { left, op, right } => {
let lval = self.eval_pixel(left, x, y)?;
let rval = self.eval_pixel(right, x, y)?;
let result = match op {
BinaryOp::Add => lval + rval,
BinaryOp::Subtract => lval - rval,
BinaryOp::Multiply => lval * rval,
BinaryOp::Divide => {
if rval.abs() < f64::EPSILON {
f64::NAN
} else {
lval / rval
}
}
BinaryOp::Power => lval.powf(rval),
BinaryOp::Greater => {
if lval > rval {
1.0
} else {
0.0
}
}
BinaryOp::Less => {
if lval < rval {
1.0
} else {
0.0
}
}
BinaryOp::GreaterEqual => {
if lval >= rval {
1.0
} else {
0.0
}
}
BinaryOp::LessEqual => {
if lval <= rval {
1.0
} else {
0.0
}
}
BinaryOp::Equal => {
if (lval - rval).abs() < f64::EPSILON {
1.0
} else {
0.0
}
}
BinaryOp::NotEqual => {
if (lval - rval).abs() >= f64::EPSILON {
1.0
} else {
0.0
}
}
BinaryOp::And => {
if lval != 0.0 && rval != 0.0 {
1.0
} else {
0.0
}
}
BinaryOp::Or => {
if lval != 0.0 || rval != 0.0 {
1.0
} else {
0.0
}
}
};
Ok(result)
}
Expr::UnaryOp { op, expr } => {
let val = self.eval_pixel(expr, x, y)?;
match op {
UnaryOp::Negate => Ok(-val),
}
}
Expr::Function { name, args } => self.eval_function(name, args, x, y),
Expr::Conditional {
condition,
then_expr,
else_expr,
} => {
let cond_val = self.eval_pixel(condition, x, y)?;
if cond_val != 0.0 {
self.eval_pixel(then_expr, x, y)
} else {
self.eval_pixel(else_expr, x, y)
}
}
}
}
pub(super) fn eval_function(&self, name: &str, args: &[Expr], x: u64, y: u64) -> Result<f64> {
let arg_vals: Result<Vec<f64>> =
args.iter().map(|arg| self.eval_pixel(arg, x, y)).collect();
let arg_vals = arg_vals?;
let result = match name {
"sqrt" => {
if arg_vals.len() != 1 {
return Err(AlgorithmError::InvalidParameter {
parameter: "sqrt",
message: "Expected 1 argument".to_string(),
});
}
arg_vals[0].sqrt()
}
"abs" => {
if arg_vals.len() != 1 {
return Err(AlgorithmError::InvalidParameter {
parameter: "abs",
message: "Expected 1 argument".to_string(),
});
}
arg_vals[0].abs()
}
"log" => {
if arg_vals.len() != 1 {
return Err(AlgorithmError::InvalidParameter {
parameter: "log",
message: "Expected 1 argument".to_string(),
});
}
arg_vals[0].ln()
}
"log10" => {
if arg_vals.len() != 1 {
return Err(AlgorithmError::InvalidParameter {
parameter: "log10",
message: "Expected 1 argument".to_string(),
});
}
arg_vals[0].log10()
}
"exp" => {
if arg_vals.len() != 1 {
return Err(AlgorithmError::InvalidParameter {
parameter: "exp",
message: "Expected 1 argument".to_string(),
});
}
arg_vals[0].exp()
}
"sin" => {
if arg_vals.len() != 1 {
return Err(AlgorithmError::InvalidParameter {
parameter: "sin",
message: "Expected 1 argument".to_string(),
});
}
arg_vals[0].sin()
}
"cos" => {
if arg_vals.len() != 1 {
return Err(AlgorithmError::InvalidParameter {
parameter: "cos",
message: "Expected 1 argument".to_string(),
});
}
arg_vals[0].cos()
}
"tan" => {
if arg_vals.len() != 1 {
return Err(AlgorithmError::InvalidParameter {
parameter: "tan",
message: "Expected 1 argument".to_string(),
});
}
arg_vals[0].tan()
}
"floor" => {
if arg_vals.len() != 1 {
return Err(AlgorithmError::InvalidParameter {
parameter: "floor",
message: "Expected 1 argument".to_string(),
});
}
arg_vals[0].floor()
}
"ceil" => {
if arg_vals.len() != 1 {
return Err(AlgorithmError::InvalidParameter {
parameter: "ceil",
message: "Expected 1 argument".to_string(),
});
}
arg_vals[0].ceil()
}
"round" => {
if arg_vals.len() != 1 {
return Err(AlgorithmError::InvalidParameter {
parameter: "round",
message: "Expected 1 argument".to_string(),
});
}
arg_vals[0].round()
}
"min" => {
if arg_vals.is_empty() {
return Err(AlgorithmError::InvalidParameter {
parameter: "min",
message: "Expected at least 1 argument".to_string(),
});
}
arg_vals.iter().copied().fold(f64::INFINITY, f64::min)
}
"max" => {
if arg_vals.is_empty() {
return Err(AlgorithmError::InvalidParameter {
parameter: "max",
message: "Expected at least 1 argument".to_string(),
});
}
arg_vals.iter().copied().fold(f64::NEG_INFINITY, f64::max)
}
_ => {
return Err(AlgorithmError::InvalidParameter {
parameter: "function",
message: format!("Unknown function: {name}"),
});
}
};
Ok(result)
}
}